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United States Patent Ofi ice Re. 24,761 .Reissuecl Jam 1 .69

COMPOSITION FOR THE PREPARATION" OF SPONGE PRODUCTS OFBUTYL RUBBER Heinz A- Pfisterer, and David W; G. Hay, Sarnia, Ontario, Canada, assignors to Polymer Corporation Limlted, Sarnia, Ontario, Canada,'a corporation of Can- No Drawing. Original No. 2,833,731, dated May 6,

1958, Serial'No. 449,275, August 11, 1954. Applicationfor reissue June 9, 1959, Serial No. 819,196

cation; matter printed in italics indicates the additions made by reissue.

This invention relates generally to the production of sponge (i.e. cellular) products from butyl rubber. Butyl rubber is a distinctive term in the. art. being a generic name applied to vulcanizable elastic copolymers, of an iso-olefin,

usually isobutylene, and small amounts of a diolefin which is generally isoprene. In any event, the iso-olefin will normally have 4 to 8 carbon atoms in the straight aliphatic chain and the diolefin will normally have 4-14 carbon atoms in the straight aliphatic chain.

Sponge rubber products may be produced either from solid rubbers or from high solids latices. In the manufacture of sponge rubber from solids, a solid blowing or gassing agent is dispersed as uniformly as possible throughout the rubbery polymer along with fillers, pigments, vulcanizers, accelerators, anti-oxidants, retarders and other compounding ingredients. The blowing or gassing agents are primarily thermally decomposable to provide a gaseous material. The sponge products may be either of the, closed cell or open cell types depending on the properties required in the product. The closed cell type is-achieved by causing some degree of vulcanization before the material is allowed fully to expand and finishing vulcanization after expansion, while the open. cell type. is prepared by'permitting the material toexpand prior to vulcanization. 'The choice of blowing agents and other compounding ingredients will be influenced by the nature of the sponge required. Sodium bicarbonate, ammonium carbonate, ammonium nitrate and many amino compounds are common blowing agents. Pine particle size sodium bicarbonate has been widely used been employed in sponge products. Sponge products produced from such stocks do not possess. good ozone resistance and, where that property is required to an appreciable degree, butyl rubber would be a logical choice. Butyl rubber is recognized for its exceptional ozone resistance and aging properties, yet, where these properties are required in sponge products, there has/been limited if any use of this. material. The art heretofore has been unable to produce acceptable butyl sponge. The application of conventional sponge compounding practices results in a sponge of poor deformation recovery due to cellular tack. Efforts to overcome this disadvantage have included the incorporation of blooming agents. The blooming agents are intended to migrate, to the surfaces, including the internal surfaces, of the vulcanized rubber larly polymers of butadiene and styrene, have generally Us... in. sun. W...-

compound and render the st r-face less tacky. Sulphur, selenium, tellurium, parafi'm waxes, fatty acid waxes and high boiling aromatic esters have-been among the blooming agents recommended. The amount of such blooming agent employed deliberately exceeds-thetolerance of the polymer for such material and blooming results. The incorporation of a paraffin oil facilitates its migration. While this is a logical approach to the problem, it has not resulted in a product enjoying anyappreciable commercial acceptance. Thebloomi-ng-inmany cases detracts from the appearance ofthe product and in any event does not result in a sponge ofsufiieient resilience to be acceptable for most purposes.

It is the object of the present invent-ion to suggest a butyl rubber composition which eliminates or substantially reduces the aforementioned disadvantages.

According to the present invention, a combination for the preparation of sponge products comprises a butyl rubber polymer, a sulphonated petroleum product and tale. The tale used will normally be all of a particle size not coarser than 300 mesh, and the tale is preferably water-ground.

The combination of the su'lphonated petroleum product and the talc is found to give to the final sponge product a surprising resiliency and excel-lent deformation recovery. The sulphonated petroleum product is preferably used in the form of the plasticizer composition marketed by R. T. Vanderbilt Co., Inc., under the name Plastogen and herein designated by that name. Plastogen is composed of 98%, selected mineral oil (about C 1.6% sulphonated petroleum product (naphthenic), and 0.4% n-butyl alcohol. In whatever form it is used, the sulphonated petroleum product is preferably incorporated in the proportion of 0.4-5.0% by weight of the polymer. The talc is preferably used inthe proportion of 60-95% by weight of the polymer.

The preparation of the sponge products will normally be effected with the use of blowing agents, as described above, and it has been found that sodium bicarbonate is the most useful of the blowing agents tested with the present invention. Sodium bicarbonate is preferably used in the proportion-of 5-20% by weight of the polymer. As will be fully realizedbypersons versed in the art, a number ofother ingredients will be used with the present composition, such ingredients including fillers, pigments, vulcaniaers, accelerators, anti-oxidants, retarders and o h om und n ingred en s T es latter, however, for .0 Par of th present in ent on.

It as beentcand ad n a eo s o us n j nction ith Pl stqsen. th p a r co po it n ma ke y R, T. Vanderbilt Co, Inc, under the name Reogen and h rei d si nat d, by tha nam Re gen s composed of seleo ted mineral oil (C 15% sulphonated petroleum product (naphthenic) and 5% n-butyl alcohol. The Reogen gives additional plasticising effect. It is found definitely disadvantageous, however, to use naphthenic base oil, paraffinic; base oil and ordinary process oil for the purpose of plasticising.

In the practice of the present invention we prefer, to employ a butyl polymer in the Mooneyviscosity range of 70-80 ML 8. Moreover, we prefer it to be a relatively fast curing polymer, i.e., substantially 1.6. mol percent unsaturation. Polymers possessing lower unsaturation may be used providing the compounding recipe and cure time are adjusted to allow for the lower rate. of cure. Polymers of higher unsaturation mayalso be. used, but lower ozone resistance may be encountered in such stocks. Polymers of higher or lower Mooney viscosity may alsobe employed, though the former may be difficult. to process and the latter will tolerate less plasticizer. The following table is indicative of the components which have been successfully employed to prepare compositions according to the present invention and indicative of certain limited ranges of proportions which have been found especially useful. Parts are by weight per 100 parts of polymer.

TABLE I Parts Butyl polymer (70-80 ML 8, 1.6 mol. percent unsat.) 100 Colour As desired Reogen -15 ZnO 5 Stearic acid 2 Antioxidant 2 Titanium dioxide 5-20 NaI-ICO (approx.) 10 Talc (300 mesh) 70-90 Plastogen 40-65 Sulphur 2.0 Mercaptobenzothiazole (as sold under the name Captax and hereinafter so designated) 1.0 Tetramethylthiuramdisulfide (as sold under the name of Tuads and hereinafter so designated) 1.5 Tellurium diethyldithiocarbamate (as sold under the name of Tellurac and hereinafter so designated) 1.5

The following are examples of the recipes and methods employed in the preparation of sponge butyl rubber products:

These components were mixed in a Banbury and on an open mill in the conventional manner, the sulphur and curing aids being added on the mill. The compound was blown and vulcanized in a mold in the conventional manner at 307 F. for 30 minutes. The vulcanized product was a highly resilient sponge possessing deformation recovery comparable to sponge products prepared from natural rubber or butadiene-styrene polymers.

Example H Parts Butyl polymer (70-80 ML 8, 1.6 mol. percent unsat.) 100 Colour 2 Xylyl mercaptan 0.35 ZnO 5 Stearic acid 2 Antioxidant 2 Titanium dioxide 10 Nal-ICO l0 Talc (water ground 300 mesh) 80 Plastogen 55 Sulphur 2 Captax 1 Tuacls 1.5 Tellurac 1.5

, 4 Compounding and vulcanization were carried out as for Example I. The vulcanized sponge product possessed excellent physical properties.

Examples III-X Eight different compositions were prepared as described below and sponge products produced therefrom in accordance with conventional procedure. Each composition was based on the following general and conventional formulation, all parts being by weight:

To these basic ingredients there were added the further ingredients specified in Table II below for each of the eight compositions denoted by Examples III-X respec tively. A sponge product was prepared from each composition according to conventional procedure and the resilience of the sponge produced is indicated in each case.

TABLE 11 Examples III IV V VI VII VIII IX X 334% Napthyl Beta Mereapten. 1 33%% Xylyl Mercaptan 1 Reogen 5 10 10 10 10 10 Plastogeu 55 55 65 55 55 Naphthenic Base Oil"... 50 Process Oil 50 ParalliuicBaseOil. 50 N aHOO 1D 10 10 10 10 10 10 10 Water-Ground Talc 80 80 80 80 80 80 Fine Soft Clay .c 80 Fine OaCO; 80 Sponge Resilience very very very very very very very very good good good poor poor poor poor poor The water ground talc was 325 mesh particle size as: sold by Eastern Magnesia Talc 00., Burlington, Vermont, U.S.A.

Examples XIXIV Table III demonstrates that butyl polymers of lower Mooney viscosity and higher and lower mol. percent unsaturation may also be employed. All examples conformed to the basic general formulation specified for Examples III-X and all further incorporated:

Reogen 10 Plastogen 55 Tale (300 mesh) 80 NaHCO, 10

Nytal tale of similar particle size has been used as a substitute for water-ground talc in some of the above examples and the results were definitely useful as compared with the results achieved from prior art methods. The results with nytal talc were not, however, as good as with water-ground talc.

We claim:

1. A composition for the preparation of sponge products, said composition comprising an elastic copolymer of a major amount of an isoolefin and a minor amount of a diolefin, 5-20% by weight of polymer of sodium bicarbonate, [0.55% by weight of polymer] an amount of a mixture of 98% selected mineral oil containing about 12 carbon atoms, 1.6% sulphonated naphthenic petroleum product and 0.4% n-butyl alcohol sujficient to bring the proportion of sulphonated naphthenic petroleum product within the range of 0.4-5.0% by weight of polymer, and 60-95% by weight of polymer of talc 6 which is substantially all of a particle size not coarser than 300 mesh.

2. A composition for the preparation of sponge products, said composition comprising an elastic copolymer of a major amount of an isoolefin and a minor amount of a diolefin, 5-20% by weight of polymer of sodium bicarbonate, [0.5-5.0% by weight of polymer] an amount of a mixture of 98% selected mineral oil containing about 12 carbon atoms, 1.6% sulphonated naphthenic petroleum product and 0.4% n-butyl alcohol, plus a mixture of 80% selected mineral oil containing about 12 carbon atoms, 15% sulphonated naphthenic petroleum product and 5% n-butyl alcohol sufiicient to bring the total amount of sulphonated naphthenic petroleum product within the range of 0.45.0% by weight of polymer, and 60-95% by weight of polymer of talc which is substantially all of a particle size not coarser than 300 mesh.

References Cited in the file of this patent OTHER REFERENCES The Vanderbilt Rubber Handbook, Ninth Edition (1948), R. T. Vanderbilt Co. (New York), page 370. 

